Phylogeny and biogeography of the toxic dinoflagellate Alexandrium

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003The incidence and known distribution of paralytic shellfish poisoning (PSP) have both increased dramatically in recent decades. A concurrent rise in bloom frequency and geographic range of PSP toxin-producing Alexandrium dinoflagellates explains the increase in PSP, but the reasons for changes in Alexandrium occurrence are unknown. This thesis explores the phylogeny, taxonomy, and biogeography of Alexandrium in light of this recent expansion. Alexandrium phylogeny was reconstructed through rDNA sequence analysis and compared to traditional morphological taxonomy. Alexandrium split into two groups, termed the α and ß clades. Interspecific relationships did not correlate with the morphological traits traditionally used to identify and group species, although other traits appeared phylogenetic ally conserved. The ability to produce toxins has been acquired and/or lost multiple times during Alexandrium evolution. Because most PSP events are caused by either the tamarensis or minutum complexes, the phylogeny, species definitions, and biogeography of each complex was examined. The morphospecies of the tamarensis complex, A. catenella, A. tamarense, and A. fundyense, did not represent valid species by the phylogenetic, biologic or morphological species concepts. Instead, five cryptic species were identified through phylogeny and mating incompatibility. A. universa and A. toxipotens contain all toxic strains, while A. mediterra, A. tamarensis and A. tasmanense contain only non-toxic isolates. Within the minutum group, A. lusitanicum and A. angustitabulatum were also not distinct species based on morphology and phylogeny while A. insuetum and A. tamutum were clearly distinct. Three new minutum group species were identified on the basis of morphology, phylogeny and prior research. Unlike the pattern found for the tamarensis complex, toxic and non-toxic A. minutum strains cannot be segregated based upon LSU sequences. The reconstructed biogeography of the tamarensis and minutum complexes indicate that both natural dispersal and human-assisted transportation of Alexandrium have caused the geographic spread. Human-assisted transport of toxic A. catenella-type cells from Asia to the Thau Lagoon, France, was demonstrated in chapter iv. This thesis demonstrates the importance of human action in the recent PSP increase, better defines species boundaries and provides an invaluable genetic database for tracking future Alexandrium spread and distinguishing between harmful and non-toxic Alexandrium blooms.Financial support was provided by the Woods Hole Oceanographic Institution, the MIT-WHOI Joint Program, a NSF doctoral fellowship, NOAA Grants No. NA960P0099, NA160P1438, NSF Grants No. OCE-9808173, OCE-9415536 and supported by the U.S. ECOHAB Program sponsored by NOAA, the U.S. EP A, NSF, NASA and ONR

Getting around the Problem... A Look at the Use of Around Constructions in Kalabari

This work investigates English constructions that employ the preposition around in relation to the Kalabari equivalents of these expressions. The work begins with a general discussion of the Kalabari language, and moves to a short talk about prototype theory. Pertinent data sets are then presented in both English and Kalabari. These data serve to support the author\u27s assumptions concerning stem forms and phonological changes within the Kalabari semantic network for around\u27 constructions, which are presented in the next section. Finally, I the author arrives at conclusions concerning constraints present in around constructions, and relates this to some universals presented in Lakoff and Johnson\u27s Metaphors We Live By

Correlating Technology Surveys and Third- and Fifth-Grade Proficiency Levels in Math and Reading throughout Tennessee.

This study used two different sets of data collected through two distinct means during the 2002-2003 school year. To fulfill the federal accountability requirements related to the distribution of monies known as EdTech (2002), the Tennessee State Department of Education required every school within districts that accepted the formula EdTech funds to complete an online survey called the EdTech Tennessee Online Technology Evaluation or E-TOTE. The E-TOTE survey collected information on a variety of topics related to educational technology including questions about teaching and learning, educators\u27 preparation and development, infrastructure, and equipment counts. The other set of data came from a new criterion-referenced portion of the otherwise norm-referenced state-mandated standardized TCAP test given to third and fifth graders to also meet No Child Left Behind accountability requirements for the subjects of math and reading. Evaluations of E-TOTE survey responses revealed that most faculty members at the 1,066 schools examined in this study reported they did not feel comfortable integrating technology to the extent necessary to create fundamental changes to traditional teacher-centered pedagogies. Related to this realization could be that few schools or districts have implemented high-quality communities of learning designed to elevate teachers\u27 levels of understanding to a sufficiently high degree as to help them feel qualified to integrate technology. Furthermore, even though the majority of the networking infrastructure within schools examined in this study seemed to be relatively robust, many reported high student-to-computer ratios often combined with long replacement cycles. Multistep hierarchical regression models were used to account for the variance in the percentage of students in third and fifth grades attaining the advanced proficiency levels in math and reading. The models accounted for a number of nontechnological school characteristics such as school population, number of minority students, number of economically disadvantaged students, and per-pupil expenditure before examining the role of the aforementioned E-TOTE topics in the final step of the regression model. No strong relationships were found to exist between the technological characteristics and the advanced proficiency levels of third or fifth graders in math or reading

SURFACE-INITIATED POLYMERIZATIONS FOR THE RAPID SORTING OF RARE CANCER CELLS

Cancer metastasis directly accounts for an estimated 90% of all cancer related deaths and is correlated with the presence of malignant cells in systemic circulation. This observed relationship has prompted efforts to develop a fluid biopsy, with the goal of detecting these rare cells in patient peripheral blood as surrogate markers for metastatic disease as a partial replacement or supplement to tissue biopsies. Numerous platforms have been designed, yet these have generally failed to support a reliable fluid biopsy due to poor performance parameters such as low throughput, low purity of enriched antigen positive cells, and insufficiently low detection thresholds to detect poor expressed surface markers of target cell populations. This work describes the development of a rapid cell sorting technology called Antigen Specific Lysis (ASL) based on photo-crosslinked polymer encapsulation to isolate tumor cells in suspension. In the first study, we characterize the chemical and structural properties of the surface-initiated polymer films formed directly on mammalian cell surfaces. Coated populations are shown to remain highly viable after coating formation. Biomolecular transport is examined though film coatings on cellular substrates using fluorescent, time-resolved confocal microscopy and diffusivity estimates are generated for these materials. In the next study, a lysis-based cell isolation platform is described in which marker positive cells can be specifically coated in a heterogeneous cell suspension. Anionic surfactants lyse virtually 100% of uncoated cells while fully encapsulated cells remain protected, and are then easily collected by centrifugation. We report that purified cells are released from polymeric coatings to yield viable and functional populations. We monitor cell response throughout the isolation process by multiple techniques, and report viability \u3e80% after the sorting process. Lastly, we examine the response of process yield on the level of photoinitiator loading on target populations. Streptavidin-fluorochrome loading was quantitatively assessed on a panel of markers, both epithelial and mesenchymal, on representative model breast and lung cancer cells. We report that ASL is fundamentally capable of achieving 50-60% yield which is promising for fluid biopsy applications. Finally, both EpCAM and metastatic targeting strategies are then compared to covalently biotinylated samples to inform future robust targeting strategies

Tunneling and nonlinear transport in a vertically coupled GaAs/AlGaAs double quantum wire system

We report low-dimensional tunneling in an independently contacted vertically coupled quantum wire system. This nanostructure is fabricated in a high quality GaAs/AlGaAs parallel double quantum well heterostructure. Using a novel flip chip technique to align top and bottom split gates to form low-dimensional constrictions in each of the independently contacted quantum wells we explicitly control the subband occupation of the individual wires. In addition to the expected 2D-2D tunneling results, we have found additional tunneling features that are related to the 1D quantum wires.Comment: 4 pages, 3 figures, submitted to APL Minor revision

Undoped Electron-Hole Bilayers in a GaAs/AlGaAs Double Quantum Well

We present the fabrication details of completely undoped electron-hole bilayer devices in a GaAs/AlGaAs double quantum well heterostructure with a 30 nm barrier. These devices have independently tunable densities of the two-dimensional electron gas and two-dimensional hole gas. We report four-terminal transport measurements of the independently contacted electron and hole layers with balanced densities from $1.2 \times 10^{11}$cm$^{-2}$ down to $4 \times 10^{10}$ cm$^{-2}$ at $T = 300 mK$. The mobilities can exceed $1 \times 10^{6}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for electrons and $4 \times 10^{5}$ cm$^{2}$ V$^{-1}$ s$^{-1}$ for holes.Comment: 3 pages, 3 figure